The present invention generally relates to processes for structuring lipids, especially unsaturated lipids, using polyamines and the composite structured products obtained thereby.
Fats are esters of glycerol with fatty acids which can be isolated from a number of plant, animal, and marine life sources. Processes for chemically synthesizing fats also are known. Triglycerides are the predominant fat constituent of most naturally-occurring fats and oils. The terms xe2x80x9coilsxe2x80x9d or xe2x80x9cfatty oils,xe2x80x9d as used herein, mean liquid fats, unless indicated otherwise.
Fats, such as triglycerides, have physical characteristics which depend upon a number of different factors, such as the types, lengths, isomeric configuration, and degree of unsaturation of the various fatty acid chain groups present, and the type and conditions of processing to which the fat is subjected. As a general rule of thumb, for a given type of fat, a saturated version thereof typically has a higher melting point than its unsaturated analogs. Generally such saturated fat molecules can fit together more closely and can form intermolecular bonds. Consequently, more energy will be required to break and melt such saturated fats. By comparison, unsaturated fats generally can not structurally fit together as well, at least partially due to the 30xc2x0 bend or xe2x80x9ckinkxe2x80x9d present at cis configuration carbon-carbon double bonds in the fatty acid chains of an unsaturated fat. This typically results in reduced intermolecular forces, and a concomitant lower melting temperature for the unsaturated fat.
Among other things, solid and semi-solid forms of fats have been used extensively in the food processing and food service industries. For example, solid and partially solid forms of fat have been used to improve the stabilities of various food products and deep frying fats. They also have been used to improve the texture and consistency of spreads, margarines, and the like. However, many forms of useful fats are obtained in oil form. These oils include, for example, many naturally occurring vegetable, animal, and fish oils. Consequently, interest has long existed in finding and developing processes for converting such fatty oils into solid or semi-solid forms. Such xe2x80x9chardeningxe2x80x9d processes decrease the proportion of liquid fat relative to solid fat in the processed fat, thereby reducing the melting point.
Hydrogenation is a known practical technique for hardening fatty oils, including unsaturated triglycerides. Hydrogenation is typically carried out catalytically under appropriate heat and pressure conditions to convert all, or at least some, of the carbon-carbon double bonds into carbon-carbon single bonds, thereby reducing the degree of unsaturation in the fat. As a result, once the hydrogenation reaction progresses sufficiently, the partially or fully hydrogenated oil is converted into a solid or semi-solid form with a higher melting temperature than the untreated precursor. Hydrogenation also renders the fat less susceptible to oxidative rancidity and increases the thermal stability of the fat.
Hydrogenation not only reduces the degree of unsaturation in the fat, but it also can result in other significant alterations in the molecular structure of the processed oil. For instance, the cis configuration of the carbon-carbon double bonds is more prevalently found in naturally-occurring fats rather than the trans configuration. However, and depending on processing conditions, hydrogenation often can result in the conversion of such cis carbon-carbon double bonds present in the fatty acid chain groups into the trans configuration. Cis or trans positional isomers, wherein one or more of the double bonds relocates to a new position along the fatty acid chain group, can also occur. Unfortunately, such structural changes resulting from hydrogenation are not necessarily benign, especially where the processed oil is destined for edible product uses.
As widely known and reported in recent years, a number of clinical and epidemiological studies have linked increased consumption of saturated fats with possible adverse health implications, especially in terms of increasing the risk of cardiovascular heart disease and/or aggravating such conditions. Replacement of saturated fats in a diet with polyunsaturated fats has been suggested to result in lower cholesterol levels, and in reducing low-density lipoprotein (LDL) levels in particular. Elevated levels of LDL cholesterol in the bloodstream are generally associated with increased risk of coronary heart disease. Additionally, high levels of trans fatty acids in a diet, whether from saturated or unsaturated fats, also have been associated with increases in blood levels of LDL cholesterol. Therefore, hardening of oils by reducing their degree of unsaturation, such as by hydrogenation, has drawbacks from at least dietary and health standpoints, not to mention the processing costs involved.
Triglycerides can also be prepared by esterification of glycerol using fatty acids. Such synthetic methods can also lead to products having some of the same problems as natural triglycerides discussed above.
As can be appreciated, their remains a need for techniques of hardening unsaturated fatty oils that avoid or significantly reduce the problems typically associated with hydrogenation. The present invention fulfills this need, as well as other objectives, by a unique process for structuring unsaturated lipids using polyamines without hydrogenation.
The present invention provides a process for treating unsaturated lipids by mixing them with an effective amount of a polyamine. An effective amount is an amount sufficient to increase the melting point of the resulting treated lipid composition to a temperature higher than that of the original untreated lipid. Generally, the practice of this invention allows a melting point of at least about 1xc2x0 C. higher than the melting point of the original lipid, preferably about 1 to about 70xc2x0 C. higher than the melting point of the original lipid, and more preferably about 5 to about 25xc2x0 C. higher than the melting point of the original lipid. As a consequence, this invention makes it possible to harden unsaturated lipids and convert them into solid or semi-solid forms having lower melting points than the untreated lipids. Moreover, this result is achieved without hydrogenation and without the dietary and health defects often associated with hydrogenation of unsaturated lipids.
The present invention also provides a composition having a new composite molecular structure composed of the unsaturated lipid and polyamine constituents of the mixture. The resulting lipid and polyamine composite molecular structure is thermally reversible and, thus, can be controlled and/or modified by the temperature (thermal energy) applied to the mixture. As an added advantage, polyamine constituents of the composite molecular structure can also provide other desirable properties to the compositions of the present invention. For instance, the polyamine can provide anti-microbial activity, preservative activity, thermal stability, and/or photo stability. In this way, the treated lipid is better protected against degradation.
The unsaturated lipids that can be treated with polyamine according to the present invention include, for example, unsaturated monoglycerides, unsaturated diglycerides, unsaturated triglycerides, fatty acids, fatty alcohols, phosphatides, sterols, fat-soluble vitamins, terpenes, and mixtures thereof. Although the present invention can be used with saturated lipids, it is generally preferred that it is used with unsaturated lipids, and even more preferably with unsaturated triglycerides, to obtain the most benefit. Preferred fatty oils used in the present invention are lipids having at least some unsaturation in at least one hydrocarbon chain. Suitable unsaturated lipids include, for example, readily available vegetable, animal, and marine oils containing long chain fatty acids. The invention is especially useful in the treatment of unsaturated triglyceride oils, polyunsaturated fatty acid oils, and other fatty acid oils.
The polyamines suitable for treating lipids, especially unsaturated lipids, according to the present invention generally include aliphatic polyamines. Especially preferred are aliphatic, linear polyamines of the general formula:
NH2xe2x80x94((CH2)pxe2x80x94(NH)qxe2x80x94(CH2)rxe2x80x94(NH)sxe2x80x94(CH2)t)uxe2x80x94A
wherein u is an integer of 1 to 5; p, r and t independently are integers of 0 to 8, with the proviso that at least one of p, r, and t is greater than or equal to 2; wherein q and s independently are 0 or 1; and wherein A is an amino group, a hydroxyl group, or a fluoro group, with the proviso that, when A is hydroxyl or fluoro, at least one of q and s is 1. In a preferred embodiment, an aliphatic polyamine entity is used for processing the lipid according to the invention. The aliphatic amine preferably is nonsubstituted in order to minimize steric effects. Especially preferred aliphatic polyamines are biocompatible, naturally occurring polyamines such as spermine, spermidine, and putrescine.
The effective amount of polyamine combined with the unsaturated lipid can vary depending on the type of polyamine and lipid involved in the combination, as long as it is sufficient to increase the melting point of the mixture to a value above that of the untreated unsaturated lipid. If the polyamine addition amount is too low, the melting point of the mixture will be that of the lipid component (or perhaps even lower on account of free polyamine present). Generally, the addition of at least about 1 percent polyamine, based on the combined weight of the polyamine and lipid, will be sufficient to provide the desired intermolecular interactions and physical changes on the lipid. Preferably the amount of polyamine added is about 1 to about 30 percent, and more preferably about 3 to about 10 percent. Preferably, the polyamine and lipid are combined without using an solvent in order to enhance direct contact between the mixed polyamine and lipid. If desired, other components such as, for example, flavorants, spices, colorants, and the like can be incorporated.
The compositions of the present invention can be prepared by simply mixing the components without elaborate or expensive process arrangements or equipment. Generally, such mixing is carried out at about 0 to about 100xc2x0 C., preferably at about 20 to about 50xc2x0 C., using simple agitation. Agitation during the initial stages of mixing is especially helpful. When performed at room temperature, the desired interaction of the polyamine and lipid may require about ten hours or more achieve the desired composite molecular structure, and thereby induce a higher melting temperature via the resulting structured lipid product. Although the temperature of the mixture can be increased above room temperature to accelerate the process, it is generally preferred that the temperature be kept at about room temperature to minimize oxidation.
The present invention also is directed to the lipid-polyamine mixtures containing the unique structured lipid products obtained by the process described herein. Additionally, the solid and semi-solid forms of the polyamine-treated unsaturated lipids prepared according to this invention are suitable for many and varied applications including, for example, food processing, food products, cosmetics, medicinal or cosmetic topical ointments, medicinal or cosmetic topical lotions, medicinal or cosmetic topical creams, personal care products, and the like.